Retired firefighters and retired police officer sued City for City's decision to reduce retirement health benefits it promised at time of their retirement. Circuit court should first determine whether case can be decided on nonconstitutional grounds, to determine whether each plaintiff has a vested right to specific health care benefits promised in collective bargaining agreement under which he retired. Court must apply presumption in favor of vesting unless contract language shows that parties did not intend vesting, or if extrinsic evidence shows no such intention, if contract is vague. (LYTTON and O'BRIEN, concurring.)